US9966963B2 - Frequency synthesizer - Google Patents

Frequency synthesizer Download PDF

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US9966963B2
US9966963B2 US15/273,746 US201615273746A US9966963B2 US 9966963 B2 US9966963 B2 US 9966963B2 US 201615273746 A US201615273746 A US 201615273746A US 9966963 B2 US9966963 B2 US 9966963B2
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clock signal
frequency
output
value
controller
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US20180091161A1 (en
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Mao-Hsuan Chou
Chih-Chiang Chang
Chung-Chieh Yang
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Taiwan Semiconductor Manufacturing Co TSMC Ltd
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Taiwan Semiconductor Manufacturing Co TSMC Ltd
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Priority to US15/273,746 priority Critical patent/US9966963B2/en
Priority to TW106115336A priority patent/TW201824750A/zh
Priority to CN201710660815.6A priority patent/CN107872224A/zh
Publication of US20180091161A1 publication Critical patent/US20180091161A1/en
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
    • H03L7/18—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop
    • H03L7/197—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop a time difference being used for locking the loop, the counter counting between numbers which are variable in time or the frequency divider dividing by a factor variable in time, e.g. for obtaining fractional frequency division
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
    • H03L7/18—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/099—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop
    • H03L7/0991—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop the oscillator being a digital oscillator, e.g. composed of a fixed oscillator followed by a variable frequency divider
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
    • H03L7/18—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop
    • H03L7/181—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop a numerical count result being used for locking the loop, the counter counting during fixed time intervals
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L2207/00—Indexing scheme relating to automatic control of frequency or phase and to synchronisation
    • H03L2207/50—All digital phase-locked loop

Definitions

  • This relates to a frequency synthesizer and more particularly to a count lock loop (CLL) frequency synthesizer which may be used in devices such as high speed circuits and/or wireless circuits.
  • CLL count lock loop
  • Electronic circuits often include a system for generating one or more known frequencies. These known frequencies are often related to clock signals.
  • Clock signals may be generated using oscillator circuits and/or a frequency synthesizer.
  • An oscillator circuit is typically capable of generating a single clock signal.
  • frequency synthesizers are typically capable of generating multiple clock signals using a single reference signal.
  • the reference signal may be generated by an oscillator circuit.
  • a typical frequency synthesizer circuit may utilize a phase-locked loop (PLL) circuit.
  • PLL circuits include a feedback loop. The loop filter of the PLL occupies a relatively large area and the loop may suffer from stability issues with 2 nd or higher order closed loops.
  • analog blocks present in typical frequency synthesizer circuits such as voltage controlled oscillators (VCO) and/or digitally controlled oscillators (DCO), may be sensitive to particular processes.
  • VCO voltage controlled oscillators
  • DCO digitally controlled oscillators
  • FIG. 1 is a schematic drawing of an example of frequency synthesizer, in accordance with some embodiments.
  • FIG. 2 is a timing diagram illustrating the operation of the frequency synthesizer of FIG. 1 , in accordance with some embodiments.
  • FIG. 3 is a schematic diagram of an example of a divider controller, in accordance with some embodiments.
  • FIG. 4 is a timing diagram illustrating the operation of the divider controller of FIG. 3 , in accordance with some embodiments.
  • FIG. 5 is an exemplary table describing the operation of the frequency synthesizer of FIG. 1 at different output frequencies, in accordance with some embodiments.
  • FIG. 6 is a timing diagram illustrating a first error reduction operation of the divider controller of FIG. 3 , in accordance with some embodiments.
  • FIG. 7 is a timing diagram illustrating a second error reduction operation of the divider controller of FIG. 3 , in accordance with some embodiments.
  • FIG. 8 is a schematic drawing of a second example of frequency synthesizer, in accordance with some embodiments.
  • FIG. 9 is an exemplary table describing the operation of the frequency synthesizer of FIG. 8 at different output frequencies, in accordance with some embodiments.
  • FIG. 10 is a flow chart illustrating the operation of an example of a frequency synthesizer described herein, in accordance with some embodiments.
  • first and second features are formed in direct contact
  • additional features may be formed between the first and second features, such that the first and second features may not be in direct contact
  • present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
  • the frequency synthesizer may be an all digital count lock loop (CLL) frequency synthesizer which may be used in devices such as high speed circuits and/or wireless circuits.
  • the frequency synthesizer may use a feed forward approach for frequency lock.
  • FIG. 1 is a schematic drawing of an example of frequency synthesizer in accordance with some embodiments.
  • the frequency synthesizer 100 illustrated in FIG. 1 may be a standalone circuit and/or may be incorporated into a larger circuit.
  • the frequency synthesizer 100 may be implemented as an integrated circuit device.
  • the frequency synthesizer 100 includes a reference oscillator (RO) 101 for generating a clock signal with a known frequency.
  • the reference oscillator 101 generates a clock signal 106 with a frequency (F RO ) of 5 GHZ.
  • the reference oscillator may generate a clock signal 106 with a frequency of 10 MHz, 100 MHz, 250 MHZ, 500 MHZ, 1 GHz, 2 GHZ, 2.5 GHz, 5 GHZ, or another suitable frequency.
  • the output frequency of the clock signal generated by the reference oscillator 101 is illustrated as clock signal 106 with frequency (F RO ).
  • the frequency synthesizer 100 also includes another input clock signal 102 with frequency (F IN ).
  • the frequency of the input clock signal 102 is also a known frequency. In the example illustrated in FIG. 1 , the frequency of the input clock signal 102 is 10 MHz. Other frequencies may also be used.
  • the reference oscillator clock signal 106 and the clock signal 102 are input to the divider controller 103 .
  • the divider controller 103 also receives a third input referred to as a multiplier (M) 104 .
  • M multiplier
  • the value of the multiplier 104 is 20. In some embodiments, other multiplier values may also be selected.
  • the divider 107 receives the clock signal from the reference oscillator 106 and the integer value Q and outputs a frequency signal that is equal to F RO /Q.
  • the duty controller 108 controls the duty cycle of the frequency signal output by the divider 107 and outputs an output clock signal 109 with a frequency (F OUT ).
  • the frequency of the output clock signal 109 is 200 MHZ.
  • the frequency synthesizer 100 includes a feed forward loop from input clock signal 106 to divider controller 103 and then to the divider 107 .
  • the feed forward loop aides with providing the divider 107 with the Q value.
  • the frequency of the input clock signal 106 may be preselected during circuit design and it may be possible to generate a desired output clock signal 109 during operation by adjusting the frequency of input clock signal 102 and the multiplier value 104 .
  • the frequency of the input clock signal 106 and the frequency of the input clock signal 102 may be preselected during circuit design and it may be possible to generate an output clock signal 109 with a desired frequency during operation by adjusting the multiplier value 104 .
  • FIG. 2 is a timing diagram illustrating the operation of the frequency synthesizer 100 of FIG. 1 in accordance with some embodiments.
  • the value N may be calculated by counting the number of cycles of the input (reference) clock signal (Fro) during one cycle of the input clock signal (Fin).
  • the frequency of the output signal (Fout) is generated by generating one pulse for every N/M cycles of the input (reference) clock signal (Fro).
  • M is equal to 20 so a total of 25 pulses are generated during the single cycle of the input clock signal (Fin).
  • the frequency of the pulses corresponds to the desired output frequency of the output clock signal (Fout) of the frequency synthesizer 100 .
  • the output frequency is 200 MHz.
  • FIG. 3 is a schematic diagram of an example of a divider controller in accordance with some embodiments.
  • the divider controller 103 illustrated in FIG. 3 may be implemented as part of the frequency synthesizer 100 illustrated in FIG. 1 (e.g., at 103 ).
  • FIG. 4 is a timing diagram illustrating the operation of the divider controller 103 of FIG. 3 in accordance with some embodiments. FIG. 4 is described together with FIG. 3 to aid in the understanding of the divider controller 103 .
  • the divider controller 103 is configured to obtain the value of N which is the ratio of the frequency of the reference oscillator input clock signal 106 and the input clock signal 102 .
  • the value of N is then divided by the multiplier value 104 to obtain the output (Q) of the divider controller 105 .
  • the frequency of the input clock signal 106 was 500 times that of the frequency of the input clock signal 102 and the multiplier value (M) was 20.
  • the first counter 201 receives the first (reference) clock signal 106 from the reference oscillator 101 as an input.
  • the frequency of the input clock signal 106 has a frequency that is multiple of the frequency of the input clock signal 102 .
  • the frequency of the input clock signal is 10 times the frequency of the input clock signal 102 . Accordingly, as illustrated, the input clock signal 106 cycles 10 times in the same amount of time that the input clock signal 102 cycles one time.
  • the ratio of these frequencies corresponds to the value of variable (N).
  • the first counter 201 increments an internal count value and outputs the count value to the comparison circuit 202 .
  • the first counter 201 increments on the leading edge of each cycle of the input clock signal 106 .
  • the first counter 201 may increment on the falling edge of the input clock signal 106 or some other metric associated with the input clock signal 106 .
  • the comparison circuit 202 receives the output of the first counter and the multiplier 104 .
  • the multiplier value is 5 (M(5)).
  • the comparison circuit 202 is configured to determine when the multiplier 104 and the first counter value are equal to one another. Accordingly, once the value of the first counter reaches 5, the output of the comparison circuit switches (e.g., from a low value to a high value). When the output of the comparison circuit 202 switches, the value within the first counter 201 is reset via a feedback loop. Additionally, the value within the second counter 203 is incremented. Turning again to FIG. 4 , the resulting timing diagram illustrates the value of the second counter 203 incrementing at the leading edge of the first counter 201 .
  • the second counter 202 outputs a value of 2 at the end of each cycle of the input clock signal. Accordingly, the value of the output Q is 2.
  • Q is the ratio of N to M which, in the case of FIG. 4 , is the ratio of 10 to 5 or 2.
  • FIG. 5 is an exemplary table describing the operation of the frequency synthesizer 100 of FIG. 1 at different output frequencies in accordance with some embodiments. As illustrated in FIG. 5 , it may be desirable for the frequency synthesizer to generate different output frequencies 109 .
  • the exemplary target output frequencies include 250, 260 270, 280, 290, and 300 MHz.
  • the frequency of the input clock signal 102 is fixed at 10 MHz and the frequency of input clock signal 106 is fixed at 5 GHz (or 5000 MHz as shown in FIG. 5 ).
  • the value of N is 500 for each of the target output frequencies.
  • the output frequency is determined as the product of the frequency of the input clock signal 102 and the multiplier 104 .
  • the desired Q value can be calculated by dividing N by M.
  • the Q values (shown as N/M in FIG. 5 ) are not always integer values.
  • the Q value desired to generate the target frequency of the output clock signal 109 may be a complex value.
  • the divider controller circuit generates the Q value using a first and a second counter. In this case, the circuit design generates integer values. Accordingly, it may be necessary for the divider controller to round the Q value to the closest integer value prior to being output. However, since the output frequency 109 is determined by dividing the reference frequency by the Q value, an error is introduced as a result of the rounding operation. This potential error value is illustrated in the last column of the table in FIG. 5 . In some embodiments, error reduction operations are performed to provide a better match for a target output frequency.
  • FIG. 6 is a timing diagram illustrating a first error reduction operation of the divider controller of FIG. 3 in accordance with some embodiments.
  • FIG. 7 is a timing diagram illustrating a second error reduction operation of the divider controller of FIG. 3 in accordance with some embodiments.
  • the error reduction operation illustrated in FIG. 6 and FIG. 7 is nearly the same operation, except in FIG. 6 , the frequency of the input (reference) clock signal 106 is decreased to reduce the output frequency error, and in FIG. 7 , the reference voltage is increased to reduce the output frequency error.
  • the frequency of the input (reference) clock signal 106 is 10 times the input frequency and the multiplier value is 3.
  • the first counter 201 has a remainder value R of 1.
  • the remainder value may be less than or more than half of the multipler value 104 .
  • the frequency of the input clock signal 106 is decreased.
  • the frequency of the input clock signal 106 may be decreased to a value that results in a remainder value R of 0.
  • the frequency of the input (reference) clock signal 106 may be decreased to nine (9) times the frequency of input clock signal 102 to reduce the remainder value R to 0. In this manner, the first counter value does not include a remainder value R.
  • the frequency of the input (reference) clock signal 106 is 10 times the frequency of input clock signal 102 and the multiplier value is 6.
  • the first counter 201 has a remainder value R of 4.
  • the frequency of the input (reference) clock signal 106 is increased until the remainder value R is reduced to 0.
  • the frequency of the input (reference) clock signal 106 is increased to twelve (12) times the frequency of the input clock signal 102 so the remainder value R is 0. In this manner, the first counter value does not include a remainder value R.
  • FIG. 8 is a schematic drawing of a second example of a frequency synthesizer in accordance with some embodiments.
  • the frequency synthesizer 300 in FIG. 8 is similar to the frequency synthesizer 100 illustrated in FIG. 1 .
  • the frequency synthesizer 300 differs from the embodiment illustrated in FIG. 1 because it includes a digitally controlled oscillator 302 which generates a digitally controlled input clock signal 303 with a frequency (F DCO ).
  • the Divider controller 103 generates a remainder value (R) 301 and communicates the remainder value 301 (or similar error information) to the digitally controlled oscillator 302 .
  • R remainder value
  • the remainder value 301 is used by the digitally controlled oscillator 302 to adjust the frequency of the digitally controlled input clock signal 303 to reduce the error of the frequency of the output clock signal 109 .
  • the digitally controlled oscillator 302 may be configured to increase and/or decrease the frequency of the digitally controlled input clock signal 303 in a predetermined value (e.g., 10 MHz, 20 MHz, 30 MHz, 40 MHz, 50 MHz, etc.) referred to as the gain (K DCO ).
  • FIG. 9 is an exemplary table describing the operation of the frequency synthesizer of FIG. 8 at different output frequencies in accordance with some embodiments.
  • the frequency of the input clock signal 102 is fixed at 10 MHz and the desired output frequency varies from 200 MHz to 300 MHz in increments of 10 MHz.
  • the initial frequency of the digitally controlled input clock signal 303 for each target output frequency is 5 GHz.
  • the frequency of the digitally controlled input clock signal 303 is adjusted up or down.
  • the adjusted digitally controlled frequency is adjusted in increments of 20 MHz.
  • the frequency error is given by K DCO ⁇ [round(N/M)]. Accordingly, the larger N/M is, the smaller the frequency error will be and the smaller K DCO is, the smaller the frequency error will be.
  • the frequency error is about 2%. This is because the frequency of the input clock signal 106 is fixed at 5 GHz and the multiplier 104 is set at a value of 3 0 . Accordingly, the actual output frequency is not the same as the target output frequency.
  • the frequency of the digitally controlled input clock signal 303 is adjusted higher by 80 MHz (4*K DCO ) to 5080 MHz. This adjustment brings the actual Q value closer to the rounded Q value of 17. Since less adjustment of Q is performed (i.e., there is less rounding error), the actual output frequency is closer to the desired output frequency of the output clock signal 109 and the error between the actual and target output frequencies is reduced.
  • the output of the divider 107 is a series of pulses at a frequency equal to the output frequency.
  • the duty controller 108 is configured to adjust the duty cycle of this signal to the desired level. For example, in some embodiments, it may be desirable for the output frequency 109 to have a duty cycle of 50% or about 50% (e.g., 45-55%). To accomplish this, the duty controller 108 extends the high level of the divider output until half of the period of the output clock signal 109 . In some embodiments, the duty controller 108 may compare the digitally controlled input clock signal and the output of the divider 107 .
  • the duty controller 108 may keep the output frequency of the output clock signal at a high level until the rising edge of the 0.5*Q+1 pulse. If the value of Q is odd, the duty controller 108 may keep the output frequency of the output clock signal at a high level until the falling edge of the 0.5*Q pulse.
  • FIG. 10 is a flow chart illustrating the operation of an example of a frequency synthesizer described herein in accordance with some embodiments. For ease of understanding, the operations of FIG. 10 are described relative to structures illustrated in FIG. 8 . But, the operations of FIG. 10 are equally applicable to other structures as well.
  • the frequency synthesizer 300 receives a digitally controlled input clock signal 303 from the digitally controlled oscillator 302 and a second input clock signal 102 at operation 1001 .
  • a multiplier value 104 is received by the frequency synthesizer 300 and, more specifically, the divider controller 103 .
  • the divider controller 103 obtains a ratio of the frequency of the digitally controlled input clock signal 303 to the frequency of the second clock signal 102 .
  • the divider controller 103 calculates the value of Q by dividing the ratio by the multiplier M.
  • the frequency of the digitally controlled clock signal 106 is divided by the Q value to obtain an output clock signal with a desired output frequency or a frequency close to the desired output frequency.
  • a duty controller 108 adjusts the duty cycle of the output clock signal to a desired duty cycle (e.g., 50%). As further illustrated in FIG.
  • the divider controller 103 also communicates error information (R) back to the digitally controlled oscillator 302 , at operation 1007 .
  • the digitally controlled oscillator 302 adjusts the frequency of the digitally controlled input clock signal 303 at operation 1008 .
  • the adjusted clock signal replaces the previous digitally controlled clock signal.
  • the frequency synthesizer described herein may benefit from more of more of the following advantages.
  • the frequency synthesizer may not include a loop filter which may reduce the area occupied by the frequency synthesizer.
  • the frequency synthesizer may not suffer from the instability issues associated with 2 nd order closed loops since the frequency synthesizer may not include a feedback loop or may only have a first order feedback loop.
  • the frequency synthesizer may be more easily implemented with standard cell designs since the frequency synthesizer is an all digital design—i.e., in some embodiments, the frequency synthesizer may not include any analog components.
  • Embodiments described herein may provide a frequency synthesizer comprising a reference oscillator configured to generate a first clock signal with a reference frequency and a divider controller configured to receive the first clock signal, a second clock signal, and a multiplier value.
  • the divider controller is configured to obtain a ratio of a frequency of the first clock signal to a frequency of the second clock signal and divide the resulting ratio by the multiplier value to obtain controller output value.
  • a divider is configured to receive the first clock signal and controller output value and output an output clock signal with a frequency equal to the frequency of the first clock signal divided by the controller output value.
  • Embodiments described herein may provide an all digital frequency synthesizer comprising a reference oscillator configured to generate a first clock signal with a reference frequency and a divider controller comprising a first counter circuit, a comparison circuit and a second counter circuit.
  • the divider controller may be configured to receive the first clock signal, a second clock signal, and a multiplier value, and may be configured to obtain a ratio of a frequency of the first clock signal to a frequency of the second clock signal and divide the resulting ratio by the multiplier value to obtain a controller output value.
  • a divider configured to receive the first clock signal and the controller output value and output an output clock signal with a frequency equal to the frequency of the first clock signal divided by the controller output value may also be provided.
  • a feedback loop configured to communicate error information from the divider controller to the reference oscillator to enable the reference oscillator to adjust the frequency of the first clock signal and reduce the frequency error between the actual frequency of the output clock signal and a desired frequency of the output clock signal may be provided.
  • Embodiments described herein may provide for a method for generating an output clock signal that includes receiving a first clock signal and a second clock signal; receiving a multiplier value; and obtaining a ratio of the frequency of the first clock signal to the frequency of the second clock signal.
  • the method may further comprise calculating a controller output by dividing the resulting ratio by the multiplier value; and dividing the frequency of the first clock signal by the controller output value to obtain an output clock signal.
  • the frequency synthesizer may further comprise a duty controller configured to obtain the output clock signal and adjust the duty cycle of the output clock signal.
  • the duty controller may be configured to adjust the duty cycle of the output clock signal to 50%.
  • the frequency synthesizer may be implemented using only digital circuit components.
  • the multiplier value may be selected such that the product of the multiplier value and the frequency of the second input clock signal is equal to the frequency of the output clock signal.
  • the output of the divider controller may be an integer value.
  • the divider controller may comprise a first counter circuit, a comparison circuit, and a second counter circuit.
  • the divider controller may be configured to communicate error information to the reference oscillator in a feedback loop to enable the reference oscillator to adjust the frequency of the first clock signal and reduce the frequency error between the actual frequency of the output clock signal and a desired frequency of the output clock signal.
  • the reference oscillator may be a digitally controller oscillator.
  • the digitally controlled oscillator may be configured to adjust the frequency of the first clock signal in predetermined frequency increments.

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TW106115336A TW201824750A (zh) 2016-09-23 2017-05-09 頻率合成器
CN201710660815.6A CN107872224A (zh) 2016-09-23 2017-08-04 频率合成器

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US10897260B2 (en) * 2016-09-27 2021-01-19 Marvell Asia Pte, Ltd. Systems and methods for performing phase error correction
TWI675280B (zh) * 2018-10-25 2019-10-21 新唐科技股份有限公司 時脈產生電路及其時脈調整方法
CN111198835B (zh) * 2018-11-16 2021-07-30 瑞昱半导体股份有限公司 时钟产生装置及时钟产生方法

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Publication number Priority date Publication date Assignee Title
US5121417A (en) * 1988-09-02 1992-06-09 Eastman Kodak Company Count-locked loop timing generator
US20110234265A1 (en) * 2010-03-25 2011-09-29 Zhibin Huang Programmable Frequency Divider
US20140176201A1 (en) * 2012-12-21 2014-06-26 Silicon Laboratories Inc. Time-interleaved digital-to-time converter
US20140327473A1 (en) * 2013-05-02 2014-11-06 Mstar Semiconductor, Inc. Method and apparatus for a programmable frequency divider

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5121417A (en) * 1988-09-02 1992-06-09 Eastman Kodak Company Count-locked loop timing generator
US20110234265A1 (en) * 2010-03-25 2011-09-29 Zhibin Huang Programmable Frequency Divider
US20140176201A1 (en) * 2012-12-21 2014-06-26 Silicon Laboratories Inc. Time-interleaved digital-to-time converter
US20140327473A1 (en) * 2013-05-02 2014-11-06 Mstar Semiconductor, Inc. Method and apparatus for a programmable frequency divider

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